In the production of a high oil containing farinaceous composition by extrusion cooking, mobility and immiscibility of the water and oil phases generally increase with increasing temperature. Additionally, the mechanical action of extruder screws tends to increase separation of oil from the remaining cookie mass. The tendency for the oil to separate is at locations within the extruder at which the components are subjected to the highest pressure. Exemplary of high pressure locations in a twin screw extruder are: (1) the space between the extruder screw tips and the die orifice, and (2) the narrowest or more restricted passageways between the left and right hand screw elements.
Oil separation under system pressure (screw or die pressure) can be manifested in extruder surging or uneven mass flow rates from the die. Upon extrusion from the die, separated oil may: (1) appear as a coating on the remaining dough mass, or (2) periodically discharge separately from the remaining dough mass. Non-homogeneous dough production and discontinuous extruder operation may thus result from oil separation. The problem of oil separation increases with increasing oil levels.
Water separation from flour, up to the boiling point of water, is generally not a problem because of the more hydrophilic properties of flour components such as gluten and starch. As flour and water temperatures are raised, increased migration of water into starch granules, protein (e.g. gluten) denaturization, and starch gelatinization tend to occur. The binding or reaction of water with flour components may promote separation of oil: (a) by making the flour components more polar or hydrophilic and (b) by creating a greater mass of hydrophilic components.
Conventional cookie production involves forming cookie dough preforms or pieces followed by baking of the pieces. Low temperatures, typically at about room temperature, are used to form the dough. The low temperature mixing generally avoids separation of shortening or fat from hydrophilic dough components. While baking temperatures in a conventional oven, such as a band oven, may promote oil separation, there is no mixing or pressing action performed at the baking temperatures. Any oil separation which may occur in such ovens does not generally interfere with continuous operability of the cookie production process as it would in a continuous cooker/extruder process.
In addition to high temperature mixing and high system pressure, the presence of sugar in a cookie dough may also increase oil and water separation. Solubilization of sugars in water increases the relative amount of the hydrophilic mass. This in turn may tend to promote oil separation.
The elimination or significant reduction of added water or a source of added water in a cooker extruder tends to reduce oil separation from hydrophilic cookie dough components at elevated temperatures. However, added water or a source of water is needed in cookie production for formability or machinability of cookie doughs into sheets or pieces at high production rates. Water also helps to disperse cookie ingredients and to promote flavor and color development.
Cooking of dough products changes the texture and the flavor of the dough. The temperatures experienced in the baking oven and in a cooker-extruder will produce many of the desirable flavors. However, the cooking temperatures will inherently destroy some of the desirable compositions in the food product. A number of additives are commonly added to dough products to improve the shelf-stability, color, and flavor of the dough product. Typically, these additives are combined during the dough mixing stage and subjected to the high cooking temperatures The high temperatures often result in a loss of the activity of the additive. Many flavoring compositions contain volatile compounds which dissipate during baking. Some antioxidants and vitamins may be destroyed during the heating step.
Efforts to overcome the loss of activity of these compounds during baking usually result in adding excessive amounts of the compound during mixing or, alternatively, applying a coating of the compound over the finished product after baking. These efforts have resulted in only limited success in obtaining satisfactory concentrations of additives. For example, many of the concentrated coatings tend to impart a bitter flavor to the food. Applying a coating of the compound does not facilitate sufficient penetration of the compound to the interior of the product and results in a high concentration on the surface and low concentration toward the center. In addition, a carrier is often needed in order to apply the compound and further tends to dilute the concentration of the compound. When an aqueous solution is sprayed onto the food product, the water must typically be removed to avoid an unacceptable moisture level on the surface. The coating compositions are typically further exposed to the atmosphere and to sunlight which may degrade or alter their activity over time. In the case of preservatives and antioxidants, it is preferable to have the compounds remain in the active form for an extended period of time, in order to prevent spoilage of the food product. Coating compositions of preservatives generally have a high initial activity, which decreases steadily as the product ages. Timed release of preservatives from a stabilized source tends to maintain a steady activity level.
Liposomes are known to be useful for encapsulating a number of components such as enzymes, cosmetics, perfumes, and pharmaceuticals. Most of the work with liposomes has been in the pharmaceutical field and has been aimed in delivering bioactive agents and drugs to a particular site in the patient. Liposomes have been used to a limited extent to deliver enzymes in cheese making.
Liposomes are essentially closed lipid bilayer membranes in the form of vesicles or sacs containing an entrapped aqueous core. Liposomes may be unilamellar or multilamellar lipid vesicles enclosing a three dimensional space. The membranes of liposomes are made up of a bimolecular layer of a lipid having a polar head and a non-polar tail. When lipids are dispersed in an aqueous solution, the polar heads of the lipids orient themselves outwardly to the aqueous solution and form a continuous outer surface. Unilamellar liposomes have a single lipid bilayer while multilamellar liposomes generally have a plurality of concentric lipid bilayers. The structure of the liposome provides a unique and convenient carrier for various components entrapped in the internal aqueous layer which is separated from the external aqueous environment.
In the process of the present invention, cookie products are produced using an extrusion cooker to promote Maillard browning and flavor development without the problems caused by the separation of oil from the remaining cookie dough mass. The extruded cookies or cookie-like products of the present invention have a cookie crumb or crumb-like structure and texture and exhibit structural integrity. The cookie-like products further contain a liposome-encapsulated additive.